MsgPack as an RPC with integrated cross platform compressed payload is useful and interesting. However when you strictly consider JSON’s format to MsgPack’s format it’s all about JSON. One thing we already know about compression is that plaintext ZIPs to about 50% compression and that binary does not compress very well at all. So compressing a JSON payload will yield some coos compression where MsgPack will not and therefore we need to compare it’s native format. And after all that I/we can read or write JSON documents easily by hand.